最新刊期
卷 39 ， 期 6 ， 2016
- 摘要：Background The proton exchange membrane fuel cell (PEMFC) is considered as one of the most promising clean energy sources in the future, because of its high energy density and simple construction.However, the large scale commercial application of fuel cell is limited by the factors such as cost, durability and reliability. Purpose For the purpose of reducing the cost and improving the performance of the PEMFC, transition metal elements alloy Pt nanoparticles (PtFe/C, PtCo/C, PtNi/C) catalysts have been studied in recent years. Methods In situ X-ray absorption fine structure (XAFS) experimental testing device for PEMFC on beamline (BL14W1) of XAFS spectroscopy at the Shanghai Synchrotron Radiation Facility (SSRF) is conducted to explore the nanostructure changes of PtCo/C during the fuel cell operation. Results In situ XAFS spectra indicts that Pt, and Co are gradually being reduced as the voltage of fuel cell decreases.Ex-situ XAFS spectra show Pt and Co did not form Pt-Co bond, but there is a strong Co-O bond and Co-O-Co bond. Conclusion The element of Co improves the performance of PtCo/C catalysts for the oxygen reduction reaction (ORR) and decreases the cost of fuel cells by regulating the electronic structure of Pt.关键词：PEMFC;In situ;XAFS;Nanostructure changes
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发布时间：2021-05-24 - 摘要：Background Anode in solid oxide fuel cell (SOFC) provides three-phase boundary (TPB) regions for electrochemical reactions and plays an active role in mass transfer, gas diffusion and isolation between different substances. Purpose During operation, the microstructure of anode will be changed.Research on microstructural evolution of SOFC anode can help us understand performance degradation of SOFC after long time operation. Methods Recently, development of X-ray nano-CT (Computed Tomography) makes it possible to nondestructively obtain the three-dimensional (3D) microstructural change of anodes subjected to no test and test for 20 h.Some quantitative analysis methods developed in house are applied to obtain key parameters of microstructures. Results Based on the reconstructions of anode 3D microstructures, some parameters of microstructures are measured, such as particle size, volume fraction of each phase and connectivity for each phase.The average particle size of Ni increases after SOFC test, while the Ni-phase connectivity and TPB density of tested anode decrease, which is caused by the aggregation and growth of Ni particles. Conclusion The data of untested and tested anode microstructures shows that the agglomeration of Ni particles occurs and internal structure of anode has changed after SOFC test, which may be a main reason causing performance degradation of SOFC during long time operation.This shows that X-ray nano-CT is a powerful tool to study energy materials and provides important data for optimizing the microstructure of anode.关键词：X-ray CT;Ni-YSZ anode;3D microstructure;Connectivity
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发布时间：2021-05-24 - 摘要：Background The 1.5-GHz 5-cell superconducting cavity designed by the Shanghai Key Laboratory of Cryogenics & Superconducting Radio Frequency Technology was optimized to accelerate a high current electron beam under continuous wave (CW) operation mode. Purpose Considering the accelerating gradient 15-20 MV·m-1, it is necessary to use twin input coupler. Methods Electromagnetic simulations of the input coupler were implemented using CST (Computer Simulation Technology), and the results showed a 18-MHz bandwidth where standing-wave ratio was better than 1.05. Power feeding by two couplers was calculated theoretically and testified on a set-up. Results Theoretical derivation and experimental results showed an enhancing when both couplers were under coupled but a reduction to the weaker coupled one when both couplers were over coupled. Results from simulations showed that transverse kick to beam can be diluted drastically even when difference of insert depths is 1mm. Conclusion Adopting twin input coupler is the only option for high average beam current CW accelerator.关键词：Twin input coupler;Coupling parameter;Coupler kick
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发布时间：2021-05-24 - 摘要：Background The crystallinity and morphology of perovskite thin film have decisive roles on its device performance in the perovskite solar cells. The perovskite thin film can be prepared using a vapor-assisted solution process, which needs to be thoroughly investigated to improve its crystallinity and morphology. Purpose We attempt to study the influence of the substrate temperature on the crystallinity and morphology of perovskite thin film prepared using the vapor-assisted solution process. Methods The perovskite thin films were prepared using a modified vapor-assisted solution process with different substrate temperatures, which were characterized by grazing incidence X-ray diffraction (GIXRD), UV-visible absorption spectrum, and scanning electron microscope (SEM). Results GIXRD analysis shows that the perovskite thin film prepared via the vapor-assisted solution process with a low substrate temperature of 70℃ exhibits favorite crystallinity with better preferential crystalline orientation than those prepared at higher temperatures (100℃ and 125℃). UV-Visible absorption spectra show the optical absorption intensity of perovskite thin film prepared with a low substrate temperature of 70℃ is the largest. SEM results support the GIXRD results, which show the perovskite crystal size and the film morphology change dramatically with increasing substrate temperature. Conclusion Based on the above results, the crystallinity, morphology and the optical absorption of perovskite thin film prepared using the modified vapor-assisted solution process are sensitive to the substrate temperature during the preparation. In general, a low substrate temperature in the modified vapor-assisted solution process is more desirable to prepare perovskite films with good crystallinity and high optical absorption.关键词：GIXRD;Perovskite thin film;Modified vapor-assisted solution process;Substrate temperature
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发布时间：2021-05-24
SYNCHROTRON RADIATION TECHNOLOGY AND APPLICATIONS
- 摘要：Background The heavy ion in the galaxy cosmos rays with extremely high energy can be fatal to the astronaut and electronic device in the spacecraft. Purpose This study aims to analyze the secondary particles produced by high energy heavy ion inject shielding materials of spacecraft. Methods Based on the Monte-Carlo method simulation software Geant4, 1-V·u-156Fe ion incident four kinds of shielding material aluminum, aluminum carbon, polyethylene and water with 1.35-g·cm-2 mass thickness have been studied. The energy deposition in the absorber and deep-dose distribution produced by the transmitted primary particles and secondary electrons, secondary neutrons, secondary protons and secondary gamma have been analyzed. All produced secondary heavy particles and energies from four kinds of shielding materials after injected high-energy 1-V·u-156Fe ion have been investigated, and the shielding performance was analyzed and compared. Results Polyethylene material absorbs the most energy, thus preservebest shielding performance whilst majority of secondary particlesand energies are produced. The energy of secondary heavy ion is quadruple of that producedby aluminum material. Conclusion Amongall the secondary particles, secondary protons and secondary heavy ionswithatom number between 22 and 26 make the maximal contributions.关键词：GEANT4;Secondary particle;Shield material;Heavy ion
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发布时间：2021-05-24 - 摘要：Background Heel effect of X-ray tube is an important factor which would affect its performance, especially for reflective X-ray tube. Purpose The study aims to research the impact of heel effect on X-ray spectral. Methods MCNP5 is adopted to create simulation model of X-ray tube and set up detector groups following different spatial position distribution. Then the performance of X-ray tube is analyzed by changing the parameters including target angle, tube voltage and target material. Results Simulation results show the impact of target angle upon X-ray spectral and X-ray intensity distribution in different spatial positions. In the final stage the impacts of target angle, tube voltage and target material on heel effect are shown. Conclusion Methods and results of this simulation provide certain theoretical guidance for the design and use of X-ray tube.关键词：Anode heel effect;X-ray tube;Spectral distribution;Monte Carlo simulation
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发布时间：2021-05-24 - 摘要：Background The spot size is of interest to the beam quality for the accelerator facility. As compared with the large accelerator scientific facility, the method to calculate the spot size is found to be different in the medical linear accelerator. The spot size in medical linear accelerator determines the penumbra field of the dose, which is important for the effective operation of medical linear accelerator. Purpose This paper aims to summarize the calculation methods of spot size, hence the discrepancy between both methods is investigated here to give a better understanding of the beam spot size. Methods The experiment setup based on the optical detection technique was presented here to given rise to the spot size results of medical linear accelerator in Shanghai United Imaging Healthcare Co., Ltd. (UIH), and a combined non-Gaussian method was proposed here to give a suitable fitting for the experiment results. Results The spot full width at half maximum (FWHM) of the 6-MeV medical linear accelerator was about 1.81 mm and 1.84 mm in x and y direction respectively, which is close to the results of calculation. Conclusion The definition of the spot size proposed here is useful for the optimizing of accelerator design, as well as the penumbra field of dose.关键词：Spot size;Gaussian fitting;Medical electron linear accelerator
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发布时间：2021-05-24
LOW ENERGY ACCELERATOR, RAY AND APPLICATIONS
- 摘要：Background The development trend of radio frequency power source systems is to replace vacuum power source devices with solid-state power amplifiers. Purpose This paper introduces the design process of a solid-state power amplifier operating at a frequency of 250 MHz. Methods A BLF578XR transistor manufactured by NXP semiconductor has been used in the amplifier model. The design of matching network adopts the method of combining transmission lines and lumped elements. The initial value in matching network was achieved through theoretical calculation, then simulated and optimized by the software ADS (Advanced Design System). Results The results of measurement showed that the output power of power amplifier module was over 850 W, power gain was over 26 dB, and power added efficiency was over 60%. Conclusion The designed parameters were all achieved in the power amplifier module, which can be further applied in scientific use.关键词：Power amplifier;Solid-state power source;Matching network
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发布时间：2021-05-24 - 摘要：Background CR-39 is an important solid-state nuclear track detector, which is widely used in neutron detection and environmental monitoring. Chemical etching is usually used to expand the track in the application of CR-39. Purpose The paper deals with chemical etching conditions of CR-39 and aims to get an optimal etching condition. Methods The three major factors to CR-39 chemical etching are etching temperature, etching time and etchant concentration (NaOH solution was used in this paper), and they were studied by an orthogonal design test. The etching temperature was 75℃, 85℃ and 95℃, respectively; the etching time was 90 min, 170 min and 240min, respectively; the etchant concentration was 5.5 mol·L-1, 6.25 mol·L-1, and 7 mol·L-1, respectively. Experimental data were analyzed with modified Grubbs rule and compared with the recommended chemical etching condition. Results The optimal chemical etching condition for CR-39 used in neutron detection is 7 mol·L-1 NaOH solution at 85℃ for 90min, which is better than the recommended chemical etching condition. Conclusion An optimal chemical etching condition for CR-39 used in neutron detection was provided, and the condition was with less time than the recommended one.关键词：CR-39;Solid state nuclear track detector (SSNTD);Neutron detection;Chemical etching;Orthogonal design test
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发布时间：2021-05-24 - 摘要：Background In order to further study the high baryon number density area in Quantum Chromodynamics Phase Diagram (QCD), compression baryon material experiment (CBM) and the construction of SIS100/300 accelerator had been launched in Antiprotons and Ion Research Center of Germany. As for time of flight (TOF) which was the sub-detector at CBM experiment, a set of data preprocessing algorithm was designed in this paper, which played a significant role in the electronic readout system of the entire TOF detector. Purpose The research aimed to design a complete set of data compression algorithm specific to data flow generated by trigger-free data acquisition system of CBM-TOF detector so as to extract data related to the particle information from such data flow and then match them into pulse signals for further data screening. Methods C programming language was adopted to write the main part of such an algorithm and compiled them into executable files. By writing script, the executable files were invoked to read raw data files of TOF detector which were input into the compression algorithm for processing. In the end, results obtained were saved in files and drawn into charts through statistics. The core of this algorithm could be classified into three parts and they were validity checking, time ordering and time over threshold checking respectively. Under the action of scripts, algorithm screening was carried out for a large amount of raw data one by one in accordance with lengths which had been determined in advance; moreover, useful data relevant with blow particles were also extracted. Results The compressed raw data were derived from beam testing of COSY in November 2011. For this algorithm, raw data volume was compressed to the maximum extent with a compression ratio of 94.5% and above; in addition, the compression algorithm didn't lose the useful data including blow information of particles. Conclusion Regarding this algorithm, not only data flow pressures on trigger-free data acquisition system link were relieved, but also valuable information was extracted from the raw data both efficiently and rapidly. Therefore, operational requirements for CBM-TOF data preprocessing were basically satisfied, which had a great significance for data reconstitution of TOF detector.关键词：TOF;Free stream data acquisition system;Data compression
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发布时间：2021-05-24
NUCLEAR ELECTRONICS AND INSTRUMENTATION
- 摘要：Background The Monte Carlo (MC) method is widely used in fission reactor design, because of its stronger geometry adaptability and the precise calculation result. The high-fidelity full core simulation demands for detailed fission reactor models, which is hard to build by manual and the conventional Computer Aided Design (CAD)-based modeling method. Purpose In order to support the rapid design of fission reactor core with MC method, and generate the detailed MC calculation models, a parameter-based and visual MC modeling method was developed in this study. Method The method can create the detailed CAD models and convert them into MC models in a high-efficiency way. Meanwhile, the huge amounts of models in fission reactor core can be managed by different segments for supporting smooth interactions. Result Furthermore, the method was validated by the test of creating the Accelerator Driven Sub-critical System (ADS) reactor models, and the results were agree very well by comparing the reference models. Conclusion Depending on the test, the detailed fission models were created more conveniently than conventional method and the numerical calculation results proved the accuracy of the new method.关键词：Monte Carlo;Fission reactor;Parameter-based and visual modeling;CAD;Calculation model;Manage by segments
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发布时间：2021-05-24
NUCLEAR PHYSICS,INTERDISCIPLINARY RESEARCH
- 摘要：Background Recently, the artificial spin ice (ASI) draws a wide attention for its exotic phenomenon and potential applications. Previous works mainly studied the Square and Kagome lattice systems, and extensive researches concentrated upon how to achieve the ground state. It turned out to be experimentally difficult to get the absolute ground state of Kagome ASI because of the high frustration. Purpose Here we propose a new structure based on Kagome lattice, which is just locally frustrated. In order to get good approximation of its ground state, we employed a Monte Carlo simulation on demagnetization process with three methods. Methods The Monte Carlo simulation was carried on a system including 21×21 cells, and an extra field had been employed to drive the spins overturning. Results & Conclusion It turned out that the rotating magnetic field was more effective to get to the ground state, and induced the emergence of various magnetic structures.关键词：ASI;Monte Carlo simulation;Demagnetization
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发布时间：2021-05-24 - 摘要：Background:Nuclear battery is a promising energy transfer device with outstanding performance. Since the 1950s, a lot of studies have been made onthe transfer of nuclear energy to electric energy through a small device. However, irradiation damage affects the efficiency and lifetime of nuclear battery. Popa-Simil proposed a theoretical model based on multi-walled carbon nanotubes (MWNTs) and metal which can achieve high energy transfer efficiency. The irradiation tolerance of MWNTs with metal embedded should be evaluated.Purpose:This studyaims to investigate the irradiation tolerance of the model of a multi-walled carbon nanotube with copper atoms embedded and compare it with one containing no cooper atoms to find out the effect of metal inside nanotubes on the irradiation tolerance.Methods:Based on empirical analytical potentials, molecular dynamics (MD) method was applied to investigate irradiation damage of the multi-walled nanotube structure with copper inside. We chose six incident energy points, which are 100eV, 200eV, 400eV, 600eV, 800eV and 1000eV, andeach energy point contained 150 independent bombarding incidents. The system was annealed after the irradiation stage then the defects were counted and analyzed.Results:Three different defect types, which are the coordination defect, sputtered atoms and perfect structure defect (PST), and the total damage (defined as the summation of these three defect amounts) were evaluated as the irradiation tolerance of the system. In metal-filled MWNT system, the number of coordination defects, PST defects and total damage are smaller than that of independent MWNT system, while the number of sputtered atoms is similar with that of independent MWNT system, while some of its mechanism is different.Conclusion:With metal inside MWNTs, the total damage by irradiation is reduced and the irradiation tolerance of this system is promoted by metal. It can be used to improve performance of nuclear batteries as major materials.关键词：Irradiation damage;Carbon nanotubes;Molecular dynamics;Nuclear battery
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发布时间：2021-05-24
NUCLEAR PHYSICS, INTERDISCIPLINARY RESEARCH
- 摘要：Background CANDLE (Constant Axial shape of Neutron flux, nuclide densities and power shape During Life of Energy produced) is a burnup strategy for Breed-and-Burn (B&B) reactors in which the effective neutron multiplication factor at an equilibrium state is equal to unity. The radius and fuel volume fraction of such a core play a very important role in the B&B mode of operation. However, using the Monte Carlo method to model a full CANDLE core for optimization costs too much computational effort and time. Purpose This study aims to assess the validity of neutron balance analysis with a simplified 1D model for determination of the maximum burnup (BU) attainable in a CANDLE mode, and then apply this 1D methodology to optimize the configurations of feed fuel and core radii for a sodium-cooled core to sustain the CANDLE mode. Methods When the maximum achievable BU of feed fuel equals the maximum burnup of the CANDLE feed fuel at equilibrium state, the keff value of the core is equal to unity. The neutron balance method with the 1D approach for various core radii and fuel volume fractions of feed fuel can provide a quick way to scope the optimized configuration. Results Neutron balance analysis with the 1D approach can provide a reasonable estimation of the maximum attainable BU of feed fuel in a CANDLE reactor, despite a small inaccuracy due to the spectrum difference between the 1D and the full core models. A small size of core and a low fuel volume fraction of feed fuel display a small value of the maximum attainable BU, which implies that it is disadvantageous to sustain a CANDLE mode. However, a too big size of core or high fuel volume fraction of feed fuel may lead tokeff>1 at equilibrium state. With the above considerations and optimization, we present a suitable core geometry and its fuel fraction to ensure the stable B&B mode of operation at equilibrium state (keff=1). Conclusion The neutron balance calculation with 1D approach can save much computational time, and the optimized configurations of feed fuel to sustain a CANDLE mode are proposed based on this methodology.关键词：CANDLE reactor;Neutron balance method;Optimized configuration;Monte Carlo method
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发布时间：2021-05-24 - 摘要：Background The system code can be used to simulate the effects of the whole system with different operation conditions, which plays an important role in dynamic analysis and safety study. As a world-known modeling tool for process simulation and optimization of oil and gas, Aspen HYSYS has the ability of secondary development for nuclear reactor simulation. Purpose The aim is to make the coupling of HYSYS and point reactor model and verify its efficiency. Methods Based on implanted and modified molten salt properties, HYSYS can show the features of molten salt accurately. A dynamic link library is built based on the point reactor model. Then the DLL (Dynamic Link Library) is called by HYSYS to calculate the reactivity which is caused by changes of operation conditions. Some operating conditions of thorium molten salt reactor are simulated and then compared with RELAP5. Results The results of HYSYS is in good agreement with that of RELAP5. Conclusion The coupled code is available in simulating molten salt-cooled system.关键词：Molten salt reactor;HYSYS;Coupling;System simulation
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发布时间：2021-05-24
NUCLEAR ENERGY SCIENCE AND ENGINEERING
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